Police investigating the murder of Pc Sharon Beshenivsky have been searching a house in Leeds as they continue to question four men about the killing.
Pc Sharon Beshenivsky was shot while on duty in Bradford last year
Detectives went to the property in Harehills on Friday afternoon, a West Yorkshire Police spokesman said.
No new arrests had been made but the search was continuing on Friday night.
Meanwhile, police have been given more time to question four men arrested on Wednesday in connection with the shooting in Bradford in November.
Magistrates have granted a warrant allowing West Yorkshire Police to detain the men until Sunday morning.
Pc Beshenivsky was shot and her colleague Pc Teresa Milburn was wounded as they responded to an armed robbery at a travel agents in the centre of Bradford on 18 November.
Yusuf Jama, 19, and Muzzaker Imtiaz Shah, 24, are charged with murder.
Earlier, two men arrested in Birmingham in January over the shooting were released on bail.
Detectives are continuing to search for 25-year-old Mustaf Jama, who is wanted in connection with the shooting.